If you’ve just started learning chemistry, the periodic table can feel overwhelming. It’s a grid full of symbols, numbers, and patterns that don’t seem to make much sense at first glance. Many students try to memorise it — and quickly get frustrated.
But here’s the key idea that most students miss:
The periodic table is not something you memorise — it’s something you understand.
Once you understand how it works, it actually becomes one of the most powerful tools in science. It helps you predict how elements behave, how they react, and even what properties they have — without needing to memorise everything.
In this guide, we’ll walk through it step-by-step, like a tutor would, so you can build a strong foundation from the beginning.
KIS Summary:
- Learn how to read and use the periodic table step-by-step.
- Understand atomic structure to predict ions, bonding, and reactivity with confidence.
- A complete beginner-friendly guide with clear diagrams and explanations
Step 1: Understand What Each Element Box Tells You
Before using the periodic table, you need to know how to extract information from a single element.
Let’s take sodium (Na) as an example.
Each element box gives you three critical pieces of information:
1. Atomic Number
This is the number of protons in the atom.
- Sodium → 11 protons
- In a neutral atom → also 11 electrons
This number defines the element.
2. Atomic Mass
This is approximately the number of protons + neutrons.
- Sodium ≈ 23 → so ~12 neutrons
3. Chemical Symbol
This is just shorthand (often from Latin names).
- Na = sodium
- Fe = iron
1. The number of electrons
2. How electrons are arranged
3. How the atom will behave chemically
Step 2: Use the Position to Determine Electron Structure
The most important rule in chemistry is:
An element’s behaviour is determined by its electrons — especially its outer (valence) electrons.
The periodic table tells you this instantly.
Period Number → Number of Electron Shells
- Period = row
- Tells you how many electron shells
Example:
Sodium is in Period 3 → it has 3 electron shells
Group Number → Valence Electrons
- Group = Column
Example:
Sodium (Group 1) → 1 valence electron
Sodium:
- 3 shells
- 1 outer electron
→ Electron configuration: 2, 8, 1
📌 This is exactly why sodium is reactive — it wants to lose that 1 electron!
Step 3: Predict Ion Formation (One of the Most Important Skills)
This is where the periodic table becomes incredibly useful.
Atoms want a full outer shell (usually 8 electrons) — this is called stability.
So they will:
- lose electrons → form positive ions
- gain electrons → form negative ions
Metals (Left Side) → Lose Electrons
Example:
Sodium (Group 1) → loses 1 electron → becomes Na⁺
Non-Metals (Right Side) → Gain Electrons
Example:
Chlorine (Group 17) → gains 1 electron → becomes Cl⁻
Shortcut Rule
| Group | Ion Formed |
|---|---|
| 1 | +1 |
| 2 | +2 |
| 13 | +3 |
| 15 | −3 |
| 16 | −2 |
| 17 | −1 |
This alone can answer a huge number of exam questions.
Step 4: Predict Reactivity
The periodic table also tells you how reactive an element is.
- Group 1 (metals): reactivity increases down the group
- Group 17 (non-metals): reactivity decreases down the group
Why This Happens
- Larger atoms → outer electrons further from nucleus
- Easier to lose (metals) or harder to gain (non-metals)
Step 5: Identify Element Type (Metal, Non-Metal, Metalloid)
A quick rule:
- Left side → metals
- Right side → non-metals
- Staircase → metalloids
From this, you can predict conductivity, bonding type and physical properties.
Step 6: Periodic Trends
Key Trends to Know
- Atomic radius → decreases across a period
- Electronegativity → increases across a period
- Ionisation energy → increases across a period
They help you predict:
- bond strength
- polarity
- reactivity
- molecular behaviour
Bringing It All Together (How to Actually Use It in Exams)
When you see an unknown element, follow this exact process:
- Find its position
- Identify group → valence electrons
- Identify period → electron shells
- Predict ion formation
- Determine metal/non-metal
- Predict bonding + reactivity
This turns the periodic table into a step-by-step problem-solving tool — not just a chart.
Final Takeaway
The periodic table is one of the most powerful tools in science — but only if you know how to use it.
You don’t need to memorise everything. You just need to understand the patterns.
Once you do, you can predict behaviour, solve problems faster, and approach chemistry with confidence.
FAQs
What is the 2, 8, 8, 18, 18 rule?
The 2, 8, 8, 18, 18 rule is a simple way to understand how electrons are arranged in shells around an atom’s nucleus. It tells you the maximum number of electrons each energy level (shell) can hold.
- 1st shell → holds up to 2 electrons
- 2nd shell → holds up to 8 electrons
- 3rd shell → holds up to 8 (for basic models)
- Higher shells → can hold more (like 18)
For example, sodium (11 electrons) is arranged as:
2, 8, 1
How do I know if an element is a metal or non-metal?
The periodic table is actually divided very clearly into regions.
- Left side → Metals
- Right side → Non-metals
- Zig-zag “staircase” line → Metalloids (in between)
A quick way to think about it:
- Metals → conduct electricity, lose electrons
- Non-metals → poor conductors, gain electrons
This matters because it helps you predict bonding and reactivity instantly.
Do I need to memorise the periodic table?
No — and this is one of the biggest misconceptions in chemistry.
You are not expected to memorise the entire table. Instead, you should understand:
- how groups relate to valence electrons
- how periods relate to electron shells
- general trends (like reactivity)
What do groups and periods mean?
- Groups (columns) → elements with similar properties
- Same number of valence electrons
- React in similar ways
- Periods (rows) → elements with the same number of electron shells
For example:
- All Group 1 elements are highly reactive metals
- All elements in Period 3 have three electron shells
Understanding this lets you quickly predict behaviour across the table.
What is the rarest element ever?
One of the rarest naturally occurring elements is astatine (At).
- It is extremely radioactive
- Only tiny amounts exist on Earth at any time
- It decays very quickly, so it’s hard to study
In fact, scientists estimate that there is less than 1 gram of astatine in the Earth’s crust at any given moment.
What Our Students & Parents Say
600+ Five-Star reviews across all our tutoring programs — hear why below !👇
